C-12M Vacuum Tube Coaxial Cable Carrier Equipment (1962)

Developing homegrown world-class technology

In 1954, NTT made the bold decision to use coaxial cables for the transmission lines that connect telephone central offices. Strict conditions, however, were imposed on the companies that were to provide the equipment. While the companies would be allowed to use technology from outside Japan, all parts had to be produced domestically and the equipment's dimensions had to meet NTT's standards. NTT's leadership would help enable Japan to construct networks using homegrown technology. At the time, Fujitsu relied entirely on technology from its partner, Siemens AG of Germany, to make transmission equipment such as the C-4M and C-6M. In 1962, however, Fujitsu independently developed the C-12M, a device that could bundle together 2700 channels, and delivered it to NTT. The fact that Fujitsu developed the C-12 at almost the same time that Siemens developed the same product was a landmark event that proved that Japan's technology was now on par with that of other countries. The C-12M was also the last transmission device to use vacuum tubes.